Simplify the following expression: $4\sqrt{125}$.
Solution: First, try to factor a perfect square out of the radical. $= 4\sqrt{125}$ $= 4\sqrt{25 \cdot 5}$ Separate the radical and simplify. $= 4\sqrt{25} \cdot \sqrt{5}$ $= 4 \cdot 5 \cdot \sqrt{5}$ $= 20\sqrt{5}$